Generalized inverse beam‐forming in applications to aeroacoustic problems.

Abstract

Current source‐detection techniques (i.e., beam‐forming) still suffer with resolving aerodynamic sources, which are typically distributed, highly directive, and partially coherent. Improvement of these tools helps us evaluate new acoustic technologies. We are developing an algorithm, called L1 generalized inverse beam‐forming, to resolve coherent/incoherent, distributed, and multipole sources. To extract each coherent signal, a cross spectral matrix is decomposed into eigenmodes. Subsequently, the complex source‐amplitude distribution that recovers each eigenmode is solved using L1‐norm generalized inverse techniques using iteratively re‐weighted least squares with reference solutions including multipoles as well as a monopole. The capabilities of the proposed algorithm are demonstrated using benchmark problems by comparing with several existing beam‐forming algorithms, and it is found that distributed sources as well as dipoles with arbitrary orientation can be identified regardless of coherency with another source. The resolution is comparable to existing deconvolution techniques, such as DAMAS or CLEAN, and the computational cost is only several times more than that of DAMAS2. The proposed algorithm has also been applied to aeroacoustic test data including noise associated with jet‐flap interaction, noise from a single round jet, and duct acoustics with flow, and these results are discussed in this talk.